Engine control to compensate for fueling dynamics

ABSTRACT

A method for calculating transient fuel wall wetting characteristics of an operating engine is described. The method accounts for cylinder valve deactivation of cylinders in the engine in calculating the dynamic fueling compensation. In one example, fuel vaporization effects from fuel puddles in deactivated cylinders is considered when calculating the fueling compensation for active cylinders.

TECHNICAL FIELD

The field of the invention relates to internal combustion engine fuelinjection compensation for fueling dynamics, wherein the fuelingdynamics are variable between cylinders and the engine operates invarious combustion modes depending on electric valve operation.

BACKGROUND OF THE INVENTION

Internal combustion engines are controlled to maintain a desired air tofuel ratio in the combustion chamber to reduce emissions. Fuel isdelivered via electronically controlled fuel injectors, modernly locatedin intake parts of the engine's cylinders, for example. However, not allinjected fuel enters the combustion chamber. Rather, some fuel is storedin the intake manifold of the engine. This phenomenon is known as “wallwetting” and various approaches are available for taking into accountthe fuel puddles in the intake manifold in controlling engine air fuelratio.

Individual cylinder compensation can also be used to develop anindividual cylinder wall wetting approach. See, U.S. Pat. No. 6,571,771.

The inventors herein have recognized a disadvantage with suchapproaches. Specifically, although the compensation is performed on anindividual cylinder basis, if used for cylinders with deactivatedcylinder valves, or cylinders operating in a variety of number ofstrokes, errors can occur. Specifically, even though cylinder valves maybe deactivated, fuel vapors can still leave the fuel puddles and migrateto other cylinders, thereby affecting the inducted air-fuel ratio. Assuch, depending on the operating mode of the engine, different physicalphenomena may occur.

SUMMARY OF THE INVENTION

Therefore, to overcome the disadvantages described above, an improvedmethod is used in which a fuel wall wetting model is used whichgenerates different compensation depending on the engine cylinderactivation, or deactivation, mode. Also, compensation can be based onwhether the engine is changing the number of strokes of the combustioncycle, with different compensation applied depending on the number ofstrokes carried out in the combustion cycle.

Further, in one example, individual cylinder fuel dynamic parameters areused to keep track of how much fuel is stored for each cylinder of theengine.

In this way, it is possible to separate the fuel puddle and vapormigration between firing, and non-firing cylinders. This allows forcompensation of the effects of cylinder valve deactivation, includingvapor migration from deactivated cylinders to active cylinders, and thusmore accurate air-fuel ratio control.

Note that fueling dynamics can include both liquid and vapor fuelretained in a puddle, or multiple puddles, in the intake system (forexample fuel retained in the intake manifold ports), wall wetting, fuelvaporization, and various other fueling dynamics.

In another example, the above disadvantages are overcome by a method forcontrolling an engine having at least a first and second cylinder, saidfirst and second cylinders having an associated first and second fuelinjector, respectively. The method comprises operating with said firstcylinder inducting air and with valves of said second cylinderdeactivated, and during said operation, injecting fuel to said firstcylinder from said first fuel injector based on evaporated fuel from anintake port of said second cylinder.

Thus, by considering fuel evaporating from a puddle of anotherdeactivated cylinder, it is possible to provide more accurate fueling toactive cylinders, thus providing more accurate air-fuel ratio control.In another embodiment, by tracking and updating vapor fuel mass andpuddle fuel mass at each combustion event to maintain the latest statusfor vapor fuel and puddle fuel at each cylinder, or intake port, it isalso possible to provide more accurate fueling to active cylinders.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages described herein will be more fully understood by readingexample embodiments illustrating advantageous operation, referred toherein as the Description of Example Embodiments, with reference to thedrawings wherein:

FIG. 1 is a block diagram of an engine illustrating various componentsrelated to the present invention;

FIG. 2A shows a schematic vertical cross-sectional view of an apparatusfor controlling valve actuation, with the valve in the fully closedposition;

FIG. 2B shows a schematic vertical cross-sectional view of an apparatusfor controlling valve actuation as shown in FIG. 1, with the valve inthe fully open position; FIG. 1 is a block diagram of an engine;

FIG. 2C is a diagram showing multiple intake ports of the engine;

FIGS. 3A–3D show experimental data for identifying dynamic fuelingparameters and validation of predicated air/fuel behavior based onidentified parameters;

FIGS. 4–6 show block diagrams of modes and routines carried out by thecontroller;

FIGS. 7A–7C show additional graphs illustrating operation of theroutines; and

FIGS. 8A–8B show additional experimental results for a variabledisplacement engine case.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENT(S)

Referring to FIG. 1, internal combustion engine 10 is shown. Engine 10is an engine of a passenger vehicle or truck driven on roads by drivers.Engine 10 is coupled to torque converter via crankshaft 13. The torqueconverter is also coupled to transmission via turbine shaft. The torqueconverter has a bypass clutch which can be engaged, disengaged, orpartially engaged. When the clutch is either disengaged or partiallyengaged, the torque converter is said to be in an unlocked state. Theturbine shaft is also known as transmission input shaft. Thetransmission comprises an electronically controlled transmission with aplurality of selectable discrete gear ratios. The transmission alsocomprises various other gears such as, for example, a final drive ratio.The transmission is also coupled to tires via an axle. The tiresinterface the vehicle to the road.

Internal combustion engine 10 comprising a plurality of cylinders, onecylinder of which, shown in FIG. 1, is controlled by electronic enginecontroller 12. Engine 10 includes combustion chamber 30 and cylinderwalls 32 with piston 36 positioned therein and connected to crankshaft13. Combustion chamber 30 communicates with intake manifold 44 andexhaust manifold 48 via respective intake valve 52 and exhaust valve 54.Exhaust gas oxygen sensor 16 is coupled to exhaust manifold 48 of engine10 upstream of catalytic converter 20. In one example, converter 20 is athree-way catalyst for converting emissions during operation aboutstoichiometry.

As described more fully below with regard to FIGS. 2 a and 2 b, at leastone of, and potentially both, of valves 52 and 54 are controlledelectronically via apparatus 210.

Intake manifold 44 communicates with throttle body 64 via throttle plate66. Throttle plate 66 is controlled by electric motor 67, which receivesa signal from ETC driver 69. ETC driver 69 receives control signal (DC)from controller 12. In an alternative embodiment, no throttle isutilized and airflow is controlled solely using valves 52 and 54.Further, when throttle 66 is included, it can be used to reduce airflowif valves 52 or 54 become degraded, or if vacuum is desired to operateaccessories or reduce induction related noise.

Intake manifold 44 is also shown having fuel injector 68 coupled theretofor delivering fuel in proportion to the pulse width of signal (fpw)from controller 12. Fuel is delivered to fuel injector 68 by aconventional fuel system (not shown) including a fuel tank, fuel pump,and fuel rail (not shown).

Engine 10 further includes conventional distributorless ignition system88 to provide ignition spark to combustion chamber 30 via spark plug 92in response to controller 12. In the embodiment described herein,controller 12 is a conventional microcomputer including: microprocessorunit 102, input/output ports 104, electronic memory chip 106, which isan electronically programmable memory in this particular example, randomaccess memory 108, and a conventional data bus.

Controller 12 receives various signals from sensors coupled to engine10, in addition to those signals previously discussed, including:measurements of inducted mass air flow (MAF) from mass air flow sensor110 coupled to throttle body 64; engine coolant temperature (ECT) fromtemperature sensor 112 coupled to cooling jacket 114; a measurement ofmanifold pressure from MAP sensor 129, a measurement of throttleposition (TP) from throttle position sensor 117 coupled to throttleplate 66; a measurement of transmission shaft torque, or engine shafttorque from torque sensor 121, a measurement of turbine speed (W1) fromturbine speed sensor 119, where turbine speed measures the speed of theturbine shaft (output of a torque converter, if equipped), and a profileignition pickup signal (PIP) from Hall effect sensor 118 coupled tocrankshaft 13 indicating an engine speed (N) and position.Alternatively, turbine speed may be determined from vehicle speed andgear ratio.

Continuing with FIG. 1, accelerator pedal 130 is shown communicatingwith the driver's foot 132. Accelerator pedal position (PP) is measuredby pedal position sensor 134 and sent to controller 12.

In an alternative embodiment, where an electronically controlledthrottle is not used, an air bypass valve (not shown) can be installedto allow a controlled amount of air to bypass throttle plate 62. In thisalternative embodiment, the air bypass valve (not shown) receives acontrol signal (not shown) from controller 12.

Referring to FIGS. 2A and 2B, an apparatus 210 is shown for controllingmovement of a valve 212 in camless engine 10 between a fully closedposition (shown in FIG. 2A), and a fully open position (shown in FIG.2B). The apparatus 210 includes an electromagnetic valve actuator (EVA)214 with upper and lower coils 216, 218 which electromagnetically drivean armature 220 against the force of upper and lower springs 222, 224for controlling movement of the valve 212. Any other alternative ofindividually controlled intake valves could also be used, if desired.

Switch-type position sensors 228, 230, and 232 are provided andinstalled so that they switch when the armature 220 crosses the sensorlocation. It is anticipated that switch-type position sensors can beeasily manufactured based on optical technology (e.g., LEDs and photoelements) and when combined with appropriate asynchronous circuitry theywould yield a signal with the rising edge when the armature crosses thesensor location. It is furthermore anticipated that these sensors wouldresult in cost reduction as compared to continuous position sensors, andwould be reliable.

Controller 234 (which can be combined into controller 12, or act as aseparate controller) is operatively connected to the position sensors228, 230, and 232, and to the upper and lower coils 216, 218 in order tocontrol actuation and landing of the valve 212.

The first position sensor 228 is located around the middle positionbetween the coils 216, 218, the second sensor 230 is located close tothe lower coil 218, and the third sensor 232 is located close to theupper coil 216.

Fueling Dynamic Model

As described above, fueling dynamics affect the amount of fuel enteringthe cylinder when conditions vary, such as by changing the amount ofinjected fuel in a PFI engine. To compensate for these dynamics, thefuel injection amount is adjusted as described in more detail below.

In general terms, a cylinder (or intake port) specific transient fuelmodel is used to derive the fuel injection compensation. The parametersχ and τ are used to describe the transient behavior of injected fuel anda fuel film at the intake port. However, a distinct set of χ and τvalues are used for each cylinder/intake port system. The model assumesa portion (1-χ) of the mass flow rate of injected liquid fuel(dm_(f)/dt) enters the cylinder, while the remainder (χdm_(f)/dt) stayson the surface of intake port/ports, which forms a liquid film or puddlemass. In addition, the vapor from fuel left over in the intake port canalso be included in this model and can contribute to the fuel mass inintake port (m_(p)), so the fuel puddle mass at the intake port can havea broader meaning.

Specifically, the compensation used herein includes the differentconditions at different cylinder/intake port systems. As such, thefueling dynamic model uses a mass balance of fuel for each intake port.The model development is shown using the equations below.

Specifically, a mass balance is written on a fuel injector/intakeport/cylinder basis. The amount of fuel entering is the mass flow rateof fuel injected from the injector (dm_(f)/dt). The mass flow rate offuel exiting the puddle is denoted as (dm_(e)/dt), which is assumedproportional (via parameter 1/τ) to the mass of fuel in the puddle(m_(p)). Writing the mass balance then gives:dm _(p) /dt=χdm _(f) /dt−dm _(e) /dtSubstituting for the flow entering the cylinder gives:dm _(p) /dt=χdm _(f) /dt−m _(p) /τHowever, while a time based model/compensation can be used, a discreteformat (event-based) can also be used in engine control applications.The event-based approach gives:m _(p)(k+1)=m _(p)(k)+χm _(f)(k)−m _(p)(k)/N _(r)where:

k is the event index, e.g., updated at every firing of the engine, orevery engine revolution, or after a certain amount of crank (or cam)shaft rotation,

m_(p) is the mass of fuel leftover in the intake port; and

χ is the portion of the injected fuel that stays in the intake porteither in liquid film form or vapor form.

m_(f) is the fuel amount injected into the intake port during a givensample period,

Nr is the characteristic time of fuel evaporation in the number ofengine events, and

τ is the time constant that describes the velocity of fuel in the intakeport leaving the intake port.

At steady state, the amount of fuel trapped in the intake port is equalto the amount of fuel leaving the intake port, which is called anequilibrium state. At an equilibrium state, the injected fuel equals theinducted fuel into the cylinder.

As indicated above, the fuel mass flow into cylinder (dm_(fcyl)/dt) thatjoins combustion process can be described via following equation as thesum of the fuel exiting the puddle, and the portion from the injectornot entering the puddle:dm _(fcyl) /dt=(1−χ)dm _(f) /dt+m _(p)/τwhere dm_(fcyl)/dt is fuel mass flow into cylinder.

Note that transportation delays in fuel injection, induction,combustion, and exhaust can be added, if desired.

The above mass balances can then be applied to a multi-port engine, andto include the sequential effect due to cycling engine operation.

In other words, engine 10 is equipped with a multi-port fuel injectionsystems so that each cylinder has an associated intake port, with anassociated fuel injector located therein. Thus, since a single modelthat attempted to lump all of the port wall wetting dynamics togethercould be inaccurate due to different effects in different cylinders, anapproach that considers the different operation of various cylinders canbe used. The cylinder or intake port-based transient fuel model is thusbased on observation of the actual operation process of a four-stroke(or multi-stroke) multi-port fuel injection engine.

As discussed above, experiments have shown that it is difficult tocharacterize transient fuel behavior by a single puddle model orso-called lumped fuel puddle model. Therefore, in one aspect,compensation that considers at least as many fuel puddles as the numberof ports or cylinders is used. Further, the interval for consecutivecombustion events is considered as one factor, if desired, to correlatetransient fuel behavior at the intake ports with air/fuel measured by anair-fuel sensor (such as, for example, an UEGO sensor, or UEGO sensorsfor V-engine at the exhaust).

As an example, an in-line four cylinders engine with a multi-port fuelinjection system is used to illustrate example operation. The liquidfuel is spread into each individual port by the associated fuel injectorat each intake port. Therefore, in this example, there are fourindividual fuel puddles considered to be located at each intake port.Note, however, that additional puddles in the ports could also be added,if desired. Also note that the following development is in the cyclebased domain (alternatively, the compensation could be event based, acrank angle based, or a time based approach could be used, if desired).

Several additional assumptions can also be used, if desired. Forexample, the difference in time for fuel puddles at each port can beneglected, and therefore each fuel puddle would have the same transientbehavior without considering the asymmetrical effect of ports,temperature difference at each port, and the difference of injectorcharacteristics. However, the difference in fuel masses could still beused to provide improved fueling compensation. Specifically, as shown inFIG. 2C, each intake port can be considered to have a different mass ofpuddle (m_(p)) based on the amount of fuel injected from the injectorassociated with that puddle (i.e., the injector associated with thatport).

From this point, the transient fuel effect observed at the exhaust wouldthen be the linear combination of each cylinder—or intake port-basedfuel puddle dynamics on the same time scale. The transient fuel dynamicsat two consecutive cylinders would shift one cylinder event.

In the four cylinders PFI engine, assuming the firing order is 1-3-4-2,gives:

$\begin{bmatrix}{m_{p1}\left( {k + 1} \right)} \\{m_{p3}\left( {k + 1} \right)} \\{m_{p4}\left( {k + 1} \right)} \\{m_{p2}\left( {k + 1} \right)}\end{bmatrix} = {\begin{bmatrix}{m_{p1}(k)} \\{m_{p3}(k)} \\{m_{p4}(k)} \\{m_{p2}(k)}\end{bmatrix} + {{\chi\begin{bmatrix}{a_{1}(i)} \\{a_{3}(i)} \\{a_{4}(i)} \\{a_{2}(i)}\end{bmatrix}}{m_{f}(k)}} - {{\frac{1}{N_{r}}\begin{bmatrix}{a_{1}(i)} & 0 & 0 & 0 \\0 & {a_{3}(i)} & 0 & 0 \\0 & 0 & {a_{4}(i)} & 0 \\0 & 0 & 0 & {a_{2}(i)}\end{bmatrix}}\begin{bmatrix}{m_{p1}(k)} \\{m_{p3}(k)} \\{m_{p4}(k)} \\{m_{p2}(k)}\end{bmatrix}}}$ ${{and}\begin{bmatrix}{m_{{fcyl\_}1}\left( {k + 1} \right)} \\{m_{{fcyl\_}3}\left( {k + 1} \right)} \\{m_{{fcyl\_}4}\left( {k + 1} \right)} \\{f_{{fcyl\_}2}\left( {k + 1} \right)}\end{bmatrix}} = {{{\left( {1 - \chi} \right)\begin{bmatrix}{a_{1}(i)} \\{a_{3}(i)} \\{a_{4}(i)} \\{a_{2}(i)}\end{bmatrix}}{m_{f}(k)}} + {{\frac{1}{N_{r}}\begin{bmatrix}{a_{1}(i)} & 0 & 0 & 0 \\0 & {a_{3}(i)} & 0 & 0 \\0 & 0 & {a_{4}(i)} & 0 \\0 & 0 & 0 & {a_{2}(i)}\end{bmatrix}}\begin{bmatrix}{m_{p1}(k)} \\{m_{p3}(k)} \\{m_{p4}(k)} \\{m_{p2}(k)}\end{bmatrix}}}$

-   -   where m_(pi) is the puddle mass at the port for cylinder i,    -   m_(fcyl) _(—) _(i) is the fuel mass that goes into cylinder i,    -   a_(j)(i)=1 when i=j, otherwise a_(j)(i)=0,

Nr is the parameter that characters the velocity of liquid fuel leavingthe puddle.

The equivalent fuel mass that goes through the exhaust port at aconjunction location(without air/fuel ratio sensor dynamic effects andmixing effects) is:

${m_{fexh}(k)} = {\sum\limits_{i = 1}^{4}{m_{fcyl\_ i}(k)}}$

If desired, sensor dynamics can also be included. For example, if usinga UEGO sensor (assumed to be a first order system with a time constantof a) adds the following dynamics:m _(fexh) _(—) _(measured)(k+1)=m _(fexh) _(—) _(measured)(k)+α⁻¹(m_(fexh)(k)−m _(fexh) _(—) _(measured)(K))

The above model can thus be used to determine the fueling dynamics foreach intake port/cylinder system. Then, these dynamics can be used tocalculate compensation to the injected fuel for each injection toprovide a more accurate overall engine air-fuel ratio from cycle tocycle during transient conditions.

However, the model is first calibrated. In one example, fuel steps areapplied, and the measured data used to calculate estimates of modelparameters to be used in the compensation algorithm.

In another example, an optimization method to test individual cylindertransient fuel behavior and identify transient fuel model parameters andUEGO sensor/exhaust mixing time constant simultaneously is used. Themethod uses an impulse fuel input. The method can be used during thecalibration phase or for adaptation during vehicle operation. Thisapproach can provide improved results since it can better compensate forUEGO sensor dynamics (which can complicate identification), and otherparasitic dynamics including multi-cylinder exhaust mixing, temperaturechanges, EGR, etc. Further, since it is difficult to separate UEGOsensor dynamics (which can vary with speed and load) from the transientfuel parameters, an impulse input can provide more accurate results.

In the case of the impulse input, at different engine operatingconditions determined by engine speed, engine load (airflow) and enginecoolant temperature, a fuel change (fuel impulse) is introduce for asingle engine event to a particular engine cylinder while maintaining aconstant airflow. As a simplification, the model can only track fuelmass left over in intake port after Intake Valve Closing (IVC), whetherit is in vapor or liquid conditions. It is not required that liquid fuelpuddle mass and fuel vapor be tracked separately, but they can be ifdesired.

Next, nominal transient fuel parameters χ,N_(r)=τ, and the UEGO sensortime constant α are simultaneously identified with a least squaresidentification procedure based on the following model:

${m_{p}\left( {k + 4} \right)} = {{m_{p}(k)} + {{\chi\left( {i(k)} \right)}\;{m_{f}(k)}} - \frac{m_{p}(k)}{N_{r}\left( {i(k)} \right)}}$${m_{fcyl}(k)} = {{\left( {1 - {\chi\left( {i(k)} \right)}} \right)\;{m_{f}(k)}} + \frac{m_{p}(k)}{N_{r}\left( {i(k)} \right)}}$m_(fexh_measured)(k + 1) = m_(fexh_measured)(k) + α⁻¹(m_(fcyl)(k − Δ D_(t)) − m_(fexh_measured)(k))where:

-   -   k is the engine event number, i(k) is the cylinder number (1, 2,        3 or 4, for a four cylinder example) into which the fuel is        scheduled during the event k (the actual fuel charge may for        example be injected into the port during the event k+2 and can        be inducted into the cylinder during the event k+4)    -   m_(f)(k) is the injected fuel mass    -   m_(p)(k) is the mass of fuel and vapor left over in the port at        intake valve closure (IVC)    -   m_(fcyl)(k) is the mass of fuel and vapor inducted into the        cylinder at IVC    -   m_(fexh) _(—) _(measured)(k) is the derived from UEGO sensor        measurement mass of fuel    -   ΔD_(t) is the delay (engine cycle delay plus transport delay)

The criterion for a good match is that the simulated model accuracy hasto agree with the measured data. Note, the same identification procedureon-line (on-board of the vehicle in the customer usage phase) can beapplied to fine-tune the transient fuel parameters in closed tosteady-state operating conditions. Note that fuel impulse applied inclose to steady-state conditions creates less of a disturbance to thecustomer than a fuel step.

With the identified parameters, the following algorithm is applied todetermine the injected fueling mass for each engine event:

${{m_{f}(k)} = {\frac{1}{1 - {\chi\left( {i(k)} \right)}}\left\{ {\frac{m_{air}(k)}{\left( {A/F} \right)_{des}} - \frac{m_{p}(k)}{N_{r}\left( {i(k)} \right)}} \right\}}},$

where (A/F)_(des) is the desired A/F and m_(air)(k) is the air amount onthe event k. Since the compensation and model are on an individualcylinder basis, different parameters can be identified for eachcylinder. In other words, different operation between cylinders can leadto different parameters. Further, whether a cylinder is active orinactive can also determine the parameters applied for that cylinder,and other cylinders.

Example experimental validation data is shown in FIGS. 3A–D.Specifically, FIG. 3A shows the injected fuel mass (impulse fuel input)to the cylinder used in exciting the system for system identification.FIG. 3B shows calculated cylinder mass in the cylinder based on theimpulse input. FIGS. 3C and 3D show a comparison between Air/Fuelresponse from identified model and test data (3C shows a response to afuel impulse and 3D shows a response to fuel step increase). The closeagreement in FIGS. 3C and 3D between the estimated and measured air tofuel ratio validates the approach. The following parameter values wereidentified for this data 1500 rpm:{circumflex over (χ)}0.293, {circumflex over (τ)}0.0912(N _(r)≈1.14cycle),{circumflex over (α)}≈0.149.

Note that in the case of an electric valve actuated engine (e.g.,electrically actuated intake valves, or both intake and exhaust valves),the above approach is especially useful due to the need to identify theindividual cylinder transient fuel behavior to enable operation invarious engine modes and to provide the individual cylindercompensation. In other words, electrically actuated valves provideseveral additional challenges for transient fuel compensation.

For example, in the case of a v-8 electric valve actuation system,various engine operating modes can be encountered, as shown in FIG. 4.The Figure shows 5 example modes, including: 8 cylinder mode (allcylinders operating) at 310; 4 cylinder mode (and 4 cylinders with atleast one deactivated intake valve) at 312; 6 cylinder mode (and 2cylinders with at least one deactivated intake valve) at 314; 2 cylindermode (and 6 cylinders with at least one deactivated intake valve) at316; and multi stroke modes (where the cylinders operate at other than4-stroke combustion, such as, for example, 6-stroke where 2 strokes areperformed with an evacuated cylinder) at 318. Alternatively, 12 strokeoperation could be used. As indicated in FIG. 4, the engine has numeroustransitions between these operating modes, each of which requiresaccurate wall wetting dynamic fuel compensation to account for thefueling dynamics associated with these transitions. As such, the abovedescribed approach is especially advantageous in such a situation.

Note that when the engine operates with variable stroke combustioncycles, the transient fuel compensation can be adjusted as discussedbelow to account for this variation. As such, different transientfueling dynamics that can occur depending on the number of strokes inthe combustion cycle can be accounted for. As such, increased air-fuelratio control both during, and when transition in and out of,multi-stroke operation is achieved.

As will be appreciated by one of ordinary skill in the art, the specificroutines described below in the flowcharts and block diagrams mayrepresent one or more of any number of processing strategies such asevent-driven, interrupt-driven, multi-tasking, multi-threading, and thelike. As such, various steps or functions illustrated may be performedin the sequence illustrated, in parallel, or in some cases omitted.Likewise, the order of processing is not necessarily required to achievethe features and advantages of the invention, but is provided for easeof illustration and description. Although not explicitly illustrated,one of ordinary skill in the art will recognize that one or more of theillustrated steps or functions may be repeatedly performed depending onthe particular strategy being used. Further, these Figures graphicallyrepresent code to be programmed into the computer readable storagemedium in controller 12.

Referring now to FIGS. 5 and 6, a routine and control block diagram aredescribed for controlling fuel injection in an electric valve actuatedengine.

Specifically, in FIG. 5, a routine is described for identifying thecylinder mode. First, in step 410, the routine reads the valve mode foreach cylinder of the engine. Then, in step 412, the routine determineswhether the engine is in a deactivation mode, where at least onecylinder valve is deactivated. If so, the routine indicates deactivationmode in step 414. Otherwise, the routine determines whether the engineis in a reactivation mode in step 416. If so, the routine indicatesreactivation mode in step 418. Otherwise, the routine indicates normalfiring in step 420.

Referring now to FIG. 6, a block diagram of a routine is shown for usingthe cylinder modes and dynamic fuelling model for an electric valveactuated engine. The block diagram has a first input set (blocks510–514) for the puddle and vapor generation management for the currentcharging cylinder. A second input set (blocks 540(1)–546(1),540(2)–546(2) (not shown), . . . 540(N)–546(N)) for vapor migration forthe non-currently charging cylinders. Then, these inputs are processedin various ways, as discussed in more detail below at blocks 518, 520,528 and 550 and used along with the desired fuel injection amount (block516) and the desired air-fuel ratio (block 522) to complete thetransient fuel model at block 524.

Finally, a correction is obtained in block 526 and output at block 530to be used in calculating the fuel injection amount to be delivered toeach cylinder. This transient fueling compensation value can be combinedwith feedback corrections from the exhaust gas oxygen sensors to allowthe combustion air-fuel ratio to approach a desired air-fuel ratio. Thefeedback can be of a proportional and integral type, or anotherappropriate form. Further, additional feedforward compensation, such asto compensate for airflow dynamics, can also be used.

The following steps illustrate this operation in detail with thecorresponding equation used. These equations correspond to thosedescribed above, but modified to take into account deactivated cylindersand vapor generation and migrations.

First, for the cylinder at the current event that is in an active,firing, mode, the fuel puddle mass at current event k, at the cylinderport i, can be calculated as:

${m_{p}\left( {k,i} \right)} = {{m_{p}\left( {{k - 1},i} \right)} + {{m_{fi}\left( {k,i} \right)}\;{\chi(i)}} - \frac{m_{p}\left( {{k - 1},i} \right)}{N_{\tau}(i)}}$

Then, the fuel mass coming into the cylinder i can be calculated as:m _(fc)(k,i)=m _(fi)(k,i)(1−χ(i))+m _(fvc)(k,i)

The fuel vapor charged into the cylinder i can be calculated as:m _(fvc)(k,i)=f(m _(airchg)(k,i),V _(runner) _(—) _(max) ,T_(airchg)(k,i),P _(airchg)(k,i),m _(fv)(k,i))

An example of this general function can be as follows. In particular,air charge mass m_(a) and air charge mass volume V_(a) can be related by

$V_{a} = {\frac{m_{a}{RT}}{P_{m}}.}$Assuming the vapor density is the maximum at the ports and zero at theend of the runner, the vapor charged into cylinder can be found as:

$m_{vc} = {0.5\left( {\frac{4m_{v}}{V_{\max}} - {\frac{2m_{v}}{V_{\max}^{2}}V_{a}}} \right)V_{a}}$where V_(max) is the maximum runner volume.

Fuel vapor generation at the current event of cylinder i can becalculated as:

${m_{fv}\left( {k,i} \right)} = {{m_{fv}\left( {{k - 1},i} \right)} + \frac{m_{p}\left( {{k - 1},i} \right)}{N_{\tau}(i)} + {\sum\limits_{\underset{j \neq i}{j = 1}}^{n}{m_{fv\_ migrated}\left( {k,j} \right)}}}$

And finally, fuel vapor generation at the non-current event of cylinderj (j≠i), can be calculated as:m _(fv)(k,j)=m _(fv)(k−1,j)−m _(fv) _(—) _(migrated)(k,j)m _(fv) _(—) _(migrated)(k,j)=f(m _(fv)(k,j),m _(airchg)(k,i),V_(runner)(j),P _(man) ,T _(man))where:

-   -   m_(fi) is the injected fuel mass    -   m_(fc) is the cylinder fuel mass    -   m_(fvc) is the cylinder fuel vapor mass    -   m_(fv) is the fuel vapor mass generated from a puddle    -   m_(fv) _(—) _(migrated) is the fuel vapor mass that migrates        from a deactivated cylinder to other cylinders    -   m_(airchg) is the cylinder air mass    -   V_(runner) _(—) _(max) is maximum volume of the runner in the        intake manifold    -   T_(airchg) is the temperature of the air charge entering the        cylinder in the intake manifold    -   P_(airchg) is the intake manifold pressure

Note that evaporated fuel can be determined based on a time sincedeactivating a cylinder, when cylinder deactivation is utilized.

Second, when the cylinder at current event is in deactivation mode, thefollowing calculations are performed. Specifically, fuel vaporgeneration at the current event of cylinder i can be calculated as:

${m_{fv}\left( {k,i} \right)} = {{m_{fv}\left( {{k - 1},i} \right)} + \frac{m_{p}\left( {{k - 1},i} \right)}{N_{\tau}(i)}}$Alternatively, a time based format can be used since vapor migration maybe more easily identified in time parameters as:

${m_{fv}\left( {k,i} \right)} = {{m_{fv}\left( {{k - 1},i} \right)} + {\frac{m_{p}\left( {{k - 1},i} \right)}{\tau(i)}\Delta\; t}}$where Δt=120/(N*N_(cyl)), N_(cyl) is the number of cylinders and N isengine speed in RPM. Again note that evaporated fuel can be determinedbased on a time since deactivating a cylinder, in one example.

When a cylinder at current event is in re-activation mode, it is similarto normal firing mode except that χ-τ or χ-N_(τ) in discrete form have acorrection due to valve temperature change because the deactivation ofthis cylinder while in normal firing mode there is no such correction.

Thus, in this example, fuel vapor charged into the cylinder iscalculated as a function of air charge mass, runner volume, enginespeed, manifold pressure and temperature, and the amount of fuel vaporin the port plus the fuel vapor migrated from other cylinders. Further,the fuel puddle mass at the port is calculated as a function of aircharge mass, engine speed, engine temperature, valve timings, valvemode, manifold pressure and temperature. Finally, the firing cylinderstatus is also identified by either reactivated cylinder or normalfiring cylinder, which indicates it has been in continuous firing statusfor a certain number of cycles.

In this way, it is possible to accurately determine the transient fueldynamics of the cylinder based on whether the cylinder is active.Further adjustments to the parameters can be included to account foreffect of variations in valve lift, valve timing, intake valve lift,exhaust valve timing, and combinations and sub-combinations thereof. Forexample, in the case where electrically actuated intake valves, andvariable cam timing exhaust valves are used, it is possible to provideaccurate transient fuel compensation to accurately maintain a desiredair-fuel ratio, even if cylinder deactivation is not used.

Simulation results are shown for an example 8 cylinder engine as shownin FIGS. 7A–C. FIGS. 7A–C show the puddle mass and vapor mass calculatedfor each cylinder during various transient engine conditions and duringvarious mode transitions of the engine. Specifically, the results areshown first during 8 cylinder mode with tip-in and tip-out changesrequested by the driver (where air charge is increased/decreased bychanging, for example, intake valve lift and/or timing). Then, atransition from 8 cylinder mode to a variable displacement mode (VDE)mode, such as 4 cylinder mode, and then back to 8 cylinder mode. Next,mode transitions are combined with tip-in and tip-out operations. Next,the engine is transitions between 8 cylinder mode and a multi-strokemode (12-stroke operation in this example), and back again. Finally, theengine is transitioned between 8 cylinder mode, variable displacementmode, and multi-stroke mode, and back again.

The Figures illustrate the transient operation that is identified usingthe approach described herein, and the corresponding compensation amountcalculated (TFC Mass).

Referring now to FIGS. 8A and 8B, additional simulation data is shown.Specifically, transient fuel compensation as described above is turnedoff in FIG. 8A, and enabled in FIG. 8B. The Figures show engine modetransitions between four and eight cylinder operation, and thecorresponding air-fuel ratio, along with other parameters. Improvedair-fuel ratio control can easily be seen in the results of FIG. 8Bcompared with that of FIG. 8A.

Although the present disclosure includes specific embodiments, specificembodiments are not to be considered in a limiting sense, becausenumerous variations are possible. The subject matter of the presentdisclosure includes all novel and nonobvious combinations andsubcombinations of the various elements, features, functions, and/orproperties disclosed herein. For example, various types of engines, suchas 4-cylinder, 6 cylinder, inline, and v-type engines can be used.

The following claims particularly point out certain combinations andsubcombinations. These claims may refer to “an” element or “a first”element or the equivalent thereof. Such claims should be understood toinclude incorporation of one or more such elements, neither requiringnor excluding two or more such elements. Other combinations andsubcombinations of features, functions, elements, and/or properties maybe claimed through amendment of the present claims or throughpresentation of new claims in this or a related application. Suchclaims, whether broader, narrower, equal, or different in scope to theoriginal claims, also are regarded as included within the subject matterof the present disclosure.

1. A method for controlling an engine having a plurality of cylinders,wherein at least one cylinder is capable of being mechanicallydeactivated, the method comprising: adjusting fuel injection amountsinjected into active cylinders of the engine based on whether said atleast one cylinder is mechanically deactivated; wherein said adjustingis at least based on a migration of fuel between said at least onemechanically deactivated cylinder and an active cylinder of the engine.2. The method of claim 1 wherein said mechanical deactivation of thecylinder is performed by deactivating an electrically actuated intakevalve.
 3. The method of claim 1 wherein said adjusting of fuel injectionamounts injected into active cylinders is performed during deactivationof said one mechanically deactivated cylinder.
 4. An article ofmanufacture comprising: a sensor for measuring an exhaust gas oxygenamount; and a computer storage medium having a computer program encodedtherein for controlling fuel injection in an internal combustion enginehaving fuel injectors coupled in intake ports thereof, said computerstorage medium comprising: code for operating the engine in at least twomodes including an active mode where the intake valves are operating andinjected fuel and air are combusted in a cylinder of the engine, and adeactivated mode where valves of the cylinder are deactivated; code foradjusting a fuel injection amount to the cylinder based on said sensorand a dynamic fueling compensation value determined based on thecylinder mode; and code for operating the engine in a third mode wherethe cylinder operates in a greater than four stroke cycle.
 5. Thearticle of claim 4 wherein said code for adjusting fuel injectioncalculated said dynamic fueling compensation on an individual cylinderbasis.
 6. The article of claim 4 wherein said code for adjusting saidfuel injection amount further adjusts said fuel injection amount basedon transitions between said first and second mode.
 7. The article ofclaim 4 wherein the engine deactivated valves in the cylinder via anelectrically actuated intake valve.